From 8a8f0a1c798363ff57d16bfcb67ff55b2f0fd311 Mon Sep 17 00:00:00 2001
From: Ankush Menat <ankush@frappe.io>
Date: Wed, 20 Jul 2022 17:51:45 +0530
Subject: [PATCH] fix: replace incorrect validation on doctype links (#17561)

---
 frappe/core/doctype/doctype/doctype.py      | 27 ++++++++++++++++-----
 frappe/core/doctype/doctype/test_doctype.py |  2 +-
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/frappe/core/doctype/doctype/doctype.py b/frappe/core/doctype/doctype/doctype.py
index 2b28373384..9a8a976b9f 100644
--- a/frappe/core/doctype/doctype/doctype.py
+++ b/frappe/core/doctype/doctype/doctype.py
@@ -17,7 +17,7 @@ from frappe.cache_manager import clear_controller_cache, clear_user_cache
 from frappe.custom.doctype.custom_field.custom_field import create_custom_field
 from frappe.custom.doctype.property_setter.property_setter import make_property_setter
 from frappe.database.schema import validate_column_length, validate_column_name
-from frappe.desk.notifications import delete_notification_count_for
+from frappe.desk.notifications import delete_notification_count_for, get_filters_for
 from frappe.desk.utils import validate_route_conflict
 from frappe.model import (
 	child_table_fields,
@@ -982,11 +982,7 @@ def validate_links_table_fieldnames(meta):
 
 	fieldnames = tuple(field.fieldname for field in meta.fields)
 	for index, link in enumerate(meta.links, 1):
-		if not frappe.get_meta(link.link_doctype).has_field(link.link_fieldname):
-			message = _("Document Links Row #{0}: Could not find field {1} in {2} DocType").format(
-				index, frappe.bold(link.link_fieldname), frappe.bold(link.link_doctype)
-			)
-			frappe.throw(message, InvalidFieldNameError, _("Invalid Fieldname"))
+		_test_connection_query(doctype=link.link_doctype, field=link.link_fieldname, idx=index)
 
 		if not link.is_child_table:
 			continue
@@ -1015,6 +1011,25 @@ def validate_links_table_fieldnames(meta):
 			frappe.throw(message, frappe.ValidationError, _("Invalid Table Fieldname"))
 
 
+def _test_connection_query(doctype, field, idx):
+	"""Make sure that connection can be queried.
+
+	This function executes query similar to one that would be executed for
+	finding count on dashboard and hence validates if fieldname/doctype are
+	correct.
+	"""
+	filters = get_filters_for(doctype) or {}
+	filters[field] = ""
+
+	try:
+		frappe.get_all(doctype, filters=filters, limit=1, distinct=True, ignore_ifnull=True)
+	except Exception as e:
+		frappe.clear_last_message()
+		msg = _("Document Links Row #{0}: Invalid doctype or fieldname.").format(idx)
+		msg += "<br>" + str(e)
+		frappe.throw(msg, InvalidFieldNameError)
+
+
 def validate_fields_for_doctype(doctype):
 	meta = frappe.get_meta(doctype, cached=False)
 	validate_links_table_fieldnames(meta)
diff --git a/frappe/core/doctype/doctype/test_doctype.py b/frappe/core/doctype/doctype/test_doctype.py
index 3a5ca4329f..a083939c94 100644
--- a/frappe/core/doctype/doctype/test_doctype.py
+++ b/frappe/core/doctype/doctype/test_doctype.py
@@ -543,7 +543,7 @@ class TestDocType(unittest.TestCase):
 
 		# check invalid doctype
 		doc.append("links", {"link_doctype": "User2", "link_fieldname": "first_name"})
-		self.assertRaises(frappe.DoesNotExistError, validate_links_table_fieldnames, doc)
+		self.assertRaises(InvalidFieldNameError, validate_links_table_fieldnames, doc)
 		doc.links = []  # reset links table
 
 		# check invalid fieldname